Despite improved methods for target ranging and fire control, conventional weaponry systems suffer from a limited effective range. The unavoidable spread of shot or projectile and difficulties in exactly ranging a target entail that hit probability declines rapidly as range increases. In such a situation, a considerable amount of ammunition and a generous amount of time are required to combat a target, factors which are not readily proffered in a combat situation.
For Forward Edge of Battle Area targets visible from the launching site, hit probability may be increased by the use of guided projectiles or missiles, for example a missile which is guided towards the target automatically or manually throughout its entire trajectory. However, such systems are apt to be extremely complex and, as a result, costly. Special launching devices are required for missiles and it must be possible for the gunnery officer to observe and track the target.
To improve hit probability and range of, for example, conventional anti-tank weapons, methods have recently been developed which are based on so-called final phase correction of the projectile. In such methods, the projectiles are discharged in a conventional manner in a ballistic trajectory towards the target. When the projectile approaches the proximity of the target, a target detector initiates the requisite trajectory correction in order that the target be hit.
The requirements for realizing final phase correction are two-fold: first, a target detector which emits a signal if the projectile is following a course towards a point beside the target; and secondly, means for correcting the trajectory of the projectile in response to the signal. The target detector may, for example, comprise a number of detector units, in which each detector is provided with an obliquely forwardly-trained field of vision such that, when the projectile approaches the target, the target scenario is scanned in an inwardly tapering helical pattern towards that point at which the projectile is currently aimed, the detectors being moreover in communication with, for example, correction motors in such a way that, if the projectile is following a trajectory to a point beside the target area (which may, for instance, be laser irradiated), ignition commands are transmitted to the correction motors such that the trajectory of the projectile is modified and the projectile is homed in on the target.
A final phase corrected, rotary projectile of this type with a correction motor comprising a number of individually selectable nozzles disposed about the periphery of the projectile and each connected to its detector is previously known from Swedish patent application No. 76.03926-2, corresponding to U.S. Pat. No. 4,116,814.
While such a homing phase-corrected projectile is both less complex to use and cheaper to manufacture than the missile which is guided onto the target automatically or manually throughout its entire trajectory, it is nevertheless necessary that the projectile or the shell be provided with complex components such as target detection device and correction motor. Furthermore, a laser transmitter is required for discharging a laser beam aimed at the target. The echo signal emitted by the laser irradiated target must be received by the target detection device and a signal must be given in response to the position of this echo signal for correcting the trajectory of the projectile.
It is previously known from Swedish patent application No. 83.01651-9 corresponding to U.S. Pat. No. 4,665,411 to reduce the spread of shot in a kill pattern for a shell by calculating, on the basis of its muzzle velocity, the point of impact of the shell and by transmitting to the shell a retardation command.
A conventional launching device, for example an artillery piece, may be employed and the shell may be provided with a conventional propellant charge. The fire command equipment must be fitted with muzzle velocity (v.sub.o) measurement equipment and the shell with a receiver for receiving retardation commands from the launching site. In the example disclosed in the above-indicated Swedish patent application, the command is transmitted to the shell in question by the intermediary of a radio link.
Even though both the receiver and braking devices in the shell may be comparatively simple, the apparatus as a whole will nevertheless be rendered relatively complex because of the ground v.sub.o measurement equipment, radar unit and radio link equipment required. Furthermore, the risk of disturbances to the system is manifest, primarily in the form of intentional jamming from the enemy.
For both missiles and the guided shells mentioned above, it is necessary that each discharged ammunition unit give a single point of impact within the target area. For a larger target area with a plurality of discrete targets, a large number of discharged shells will then be required for effectively countering and combating the target regions. As a result, it is also previously known to employ so-called submunition units which are discharged in a conventional manner in a ballistic trajectory towards the target area. After the shell canister has reached the target area, a number of submunition units are released. The submunition units are provided with target detector devices and, by imparting to the target detector device a wobbling, precession or helical motion, these can overfly the ground area under detection. On detection of a target, a projectile-forming hollow charge is initiated which has a penetration of large explosive force. The number of submunition units which may be accommodated in the canister depends upon the caliber and extraneous design of the system, for example the retardation and rotation devices of the submunition.
The target detection device may be of the IR type, but other types of target detectors may be employed, for example target detectors based on millimeter waves, or be of the magnetic or optic type. Combinations of target detectors are also conceivable. The target detector senses the target area and the detector signal is analyzed so as to distinguish between a target, for example an armored vehicle, and its background. When the target detector has revealed the target, the warhead is initiated.
Prior art brake rotation devices for realizing the sensing motion are often of the parachute type, but other devices employing mechanical vanes are also previously known. Thus, the submunition may be provided with an asymmetric parachute which imparts the desired rotation for the scanning operation, or alternatively the submunition may be of such aerodynamic design as to realize the requisite rotation. The drawback inherent in employing parachutes is that a relatively large space is then required in the shell canister, which reduces the number of submunition units in the canister.
As examples of prior art submunition systems, mention might be made of the American Sense and Destroy Armor system employing a 15.5 cm caliber shell canister developed by Avco Systems Division, USA. The Sense and Destroy Armor canister contains four discrete submunition units which are ejected from the base plane of the canister when the canister has reached the target area. As a result of the natural rotation of the submunitions on separation and by the provision of a so-called "maple seed wing" a helical scanning of the target area will be obtained.
The skilled reader of this specification is further referred to GB-PS 2 090 950 and DE-PS 3 323 685. This latter patent specification discloses a system in which the fall speed and direction of movement of the submunitions are regulated by an asymmetric parachute and in which the rotation requisite for the scanning operation is realized by a drive thrust motor.
Drawbacks common to the prior art systems are their high degree of complexity and the difficulty in imparting to the submunition a controlled fall speed and rotation.